Particle melting, flattening, and stacking behaviors in induction plasma deposition of tungsten

Particle melting, flattening, and stacking behaviors during induction plasma deposition of refractory tungsten were studied for land based turbine engine application. Scanning electron microscopy was used to observe the morphology of particles and splats as well as to examine the microstructure of tungsten deposit. Three kinds of pores were found in the deposit, i.e., large pores with d > 10?μm, medium pores in the range of 1～ 10?μm, and small pores with d < 1?μm. Both optimized plasma spray condition and use of spherical powder with a narrow particle size distribution are important in the elimination of large and medium pores and have significant influences on the formation of dense tungsten deposit. Highly dense tungsten deposit was obtained through complete melting, sufficiently flattening, and regularly stacking of tungsten particles.